Neurons of the entorhinal cortex are at the intersection of two neuronal circuits, a "locational" circuit comprised of entorhinal and hippocampal neurons, and a "directional" circuit which includes entorhinal and other retrohippocampal neurons. The goal of this project is to examine properties of deep layer entorhinal neurons and their connectivity with elements of both the directional and locational circuits. Specifically, we will focus on the inputs from subiculum and presubiculum to deep layer medical entorhinal neuronsin rat brain slices. Fundamental data needs to be acquired: 1) cell shape and dendritic extent; 2) basic membrane properties; 3) target neurons of the two inputs; 4) functional nature of each input (i.e. excitatory or inhibitory); and 5) possible convergence of subicular and presubicular inputs into single entorhinal neurons. Perhaps surprisingly, these studies have not been done. Intracellular recording techniques in brain slices will be used t acquire these data. The techniques are well established in the sponsor's laboratory. The project is straightforward for training in the sense that the data are not difficult to obtain. However, since it is a project intended to collect some of the most basic information about a brain region, there is considerable latitude to focus experimental emphasis on a particular discovery made along the way.